Re: difference in maximum color depth in Debian vs Mac OS?
On Sat, Jan 29, 2005 at 02:31:40AM -0300, Fernan Aguero wrote:
> Hi!
>
> I've had Debian woody (3.0r1) installed on my Power
> Macintosh 7200/75 for a while. Over time, and after reading
> different suggestions posted online, I've tried different
> things to make X under Debian use a higher resolution and
> color depth than the common (low) denominator of 640x480 @
> 256 colors.
>
> I've provided kernel arguments in BootX
> (platinumfb:vmode:13,cmode:16), and also played with
> XF86Config-4.
>
> I can make debian use a color depth of 16 at 640x480, and I
> can also make debian use a resolution of 832x624, but at a
> color depth of 8.
>
> The Mac OS, OTOH can do 832x624 @ thousands of colors (16).
>
> Recently I discovered fbset. I installed it and this is what
> it reported for my system when run with no arguments:
>
> mode "832x624-75"
> # D: 57.597 MHz, H: 49.997 kHz, V: 74.959 Hz
> geometry 832 624 832 624 8
> timings 17362 208 48 39 1 64 3
> rgba 8/0,8/0,8/0,0/0
> endmode
>
> After reading the man page I added this mode to
> /etc/fb.modes (but without the line for "rgba") and
> tried to now use fbset:
>
> debian:~# fbset -fb /dev/fb0 -depth 16 "832x624-75"
> platinum_var_to_par, not enough ram for vmode 13, cmode 1.
> platinum_set_var: error calling platinum_var_to_par: -22.
> ioctl FBIOPUT_VSCREENINFO: Invalid argument
>
> So now, as before, I'm unable to swith to a higher color
> depth at this resolution. But now at least I have an error
> message. Is there any reason for this "not enough ram"?
>
> The VRAM of this Macintosh is 1MB (expandable to 4MB I
> believe). However what I fail to understand is why the Mac
> OS is able to get a higher color depth than debian/linux on
> the same hardware.
I have similar problems, but I do have understanding of the issues at
hand and I think I know why the following failed for you.
> debian:~# fbset -fb /dev/fb0 -depth 16 "832x624-75"
The problem is the speed of the graphic chip, not lack of RAM. I have
a Macintosh Performa 5400 with the valkyrie graphic chip and if it the
same as yours, MacOS cannot give 16 bpp at that mode, it only
handles 16 bpp at 800x600@60HZ.
:~# fbset -i
mode "800x600-60"
# D: 40.000 MHz, H: 37.879 kHz, V: 60.317 Hz
geometry 800 600 800 600 16
timings 25000 72 56 23 1 128 4
hsync high
vsync high
rgba 5/10,5/5,5/0,0/0
endmode
Frame buffer device information:
Name : valkyrie
Address : 0xf1001000
Size : 960000
Type : PACKED PIXELS
Visual : DIRECTCOLOR
XPanStep : 0
YPanStep : 0
YWrapStep : 0
LineLength : 1600
MMIO Address: 0xf130a000
MMIO Size : 64
Accelerator : No
It *might* be possible to get 832x624@16bpp but at a lower refresh
rate.
--
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